Transitions Studies in Flowering Plants

by Rolf Baumberger

SUMMARY 2020

In our search for the ultimate genetic mechanism of the already described morphologically rapidly changing ecotypes in the genus Diplacus (Mimulus aurantiacus) see: DIPLACUS 1-4 we seem to have come closer.

By "rapidly changing" is meant within ten to 15 years.

Is the plasticity of the flowers only morphologically or also genetically fixed?

It is also genetically expressed.

How do we imagine that?

Within the coding sequences (exons), little seems to be changed (with the exceptions of Tf MaMyb2) between yellow and red ecotypes.

The situation is different when the flanking introns of the relevant transcription factors are investigated in more detail. Especially the MBW-complex and the flower size controlling gene bHLH79 are different. There are TATA and TCTC-coding inclusions that are differently configured in red, yellow, and flowers in transition.

These additional inclusions may act as expression boosters or inhibitors of the surrounding genes. Such inclusions are, at least hypothetically, dynamically altered when necessary.

Evolution in these flowers is mainly related to gene regulation, which alters in the context of environmental demand and is hereditary.

The reason is that the altered booster information on the DNA changes the genome to a small extent. Besides, it is assumed that the epigenetic information also alters.